Spider Tales 6: Orange Bitey Thing

Most of the countless spider myths circulating around are about wild spiders. 
With a few exceptions (such as the mostly false idea that a spider found inside a building can't survive if relocated outside), these myths are also mainly found among people who fear or dislike spiders, often largely consolidating their loathing of these arachnids.

It may be surprising, then, to realise that even circles where spiders are admired and appreciated aren't immune to false beliefs and urban legends. It's hard to imagine a community that loves them more than tarantula keepers; yet, even there, myths and scaremongering occasionally show their ugly faces.  

A few species, although popular in the hobby, have quite a sinister reputation due to their defensive attitude and nasty bites. One, in particular, stands out. 

Pterinochilus murinus has been a staple in the tarantula hobby for decades. Its gorgeous colours and patterns, many different colour forms, as well as its ease of care, make this species immensely popular among keepers. Yet, this popularity is tainted by a fearsome reputation; this spider is often depicted as extremely defensive, sometimes downright aggressive and almost acting like it wants to bite. There are people out there who go as far as describing it as dangerous, and some who swear they'll never ever keep this species. Its attitude is so notorious, in fact, that some hobbyists have parodied the initials of it common name, "Orange Baboon Tarantula", to instead affectionately nickname it "Orange Bitey Thing".

A permanently enraged, aggressive spider, with a nasty venom it's always itching to use: that's how many tarantula enthusiasts describe  P.murinus

 

On the other hand, a large and growing proportion of the tarantula keeper community reports a diametrically opposing experience with this species: they describe a tarantula which, while definitely fast and skittish, is actually quite calm and manageable, and only rarely reacts defensively. It is interesting to note that the latter account are mostly recent, while those describing a highly ornery animal are typically much older (excluding, of course, those from people who have never kept this species and are only repeating what they've heard). It's almost as if something changed over time... But what? 

Recent research and multiple independent setup experiments by keepers may have shed light on this question: they suggest the cause may not be the spider itself, but the husbandry. Maybe the infamous OBT is not a monster after all... Just another misunderstood animal whose needs used to be unmet.

Exaggerated but not totally undeserved 

First, let's clarify that even though it is hugely overblown, the OBT's fearsome reputation isn't baseless. Of the hundreds of Theraphosidae (tarantula) species kept by hobbyists, it is one of the most commonly implicated in bite records. Pterinochilus is one of the three genera most commonly recorded biting people in captive settings, behind Grammostola and Poecilotheria, while being significantly less widespread in the hobby than the latter. As the other Pterinochilus species (such as P.lugardi, P. chordatus and P.lapalala) are fairly recent additions to the pet trade, P.murinus has been in the hobby for decades, so it is likely that these bite records are mostly, if not solely, from murinus. 
There is, thus, a foundation to its notoriety as a frequent biter. Regardless of the circumstances and reasons, keepers have been bitten by P.murinus, more than by other species. This suggests that under certain conditions at least, the "orange bitey thing" can indeed be prone to biting.

In terms of bite cases from captive spiders on keepers, Pterinochilus is one of the most commonly implicated genera

The situation regarding the potency of its venom paints a similar picture: an exaggerated, but not groundless reputation. P. murinus is often claimed to have very potent venom, and its bite is not infrequently described as "dangerous". 
This largely stems in the confusion between "dangerous" and "medically significant"; and while calling it dangerous is a bit of a stretch, it is undeniably medically significant. 
Intense local pain, local swelling, sometimes radiating through the limb, stiffness in the bitten part, and muscle cramping are among the common effects of its bite. These effects usually last several hours to several days. A severe case, apparently requiring hospital care with potential loss of consciousness, is mentioned in the literature, although it is unfortunately not described in detail. It is unclear, because of the phrasing, whether this case had the same symptoms as the other severe ones listed in the study (caused by Poecilotheria), or if it was different.

Thus, numbers indicate OBTs do indeed bite their keepers, or at least some keepers, more than most other tarantula species do. On top of that, the bite itself is unpleasant and can, albeit rarely, require medical attention. These two realities have forged the image of a spider that does not allow much of a margin for error, and consolidated a fear which, although hugely overblown, is not entirely groundless.

The spider's fault or the keeper's fault? 

While this spooky reputation is still very much alive and, as we've seen, not entirely undeserved, many keepers (including yours truly, happy keeper of two beautiful females) have a completely different experience with this species. They describe a spider which, while fast and skittish, hardly ever shows defensive behaviours, and will always pick flight over fight if given the opportunity. Many even report not having ever seen an unprovoked threat pose from their OBT. A far cry from the "aggressive", "bitey" beast it is often portrayed as.  
Pterinochilus murinus has never been as popular in the hobby as it is nowadays; coincidentally, there has never been more people claiming its reputation is overblown or even false.

Skittish and fast, sure, but not particularly defensive; that's how many keepers describe the OBT nowadays

It is worth mentioning P. murinus has been in the pet trade for a very long time. It was one of the very first "baboon spiders" (African tarantulas) to be introduced in the hobby, and has been around for more than forty, possibly even fifty years, or even more. 
Over these decades, the standards of husbandry in the tarantula hobby have evolved considerably. At the time P.murinus was first imported into the pet trade, many husbandry practices considered standard then are now considered outdated, and were directly taken from reptile keeping (where many of these practices are also considered outdated nowadays); tarantulas were relatively new, and their needs and behaviours were still poorly known.

One of such practices was to keep tarantulas in enclosures as bare as possible, with just a moderately thick layer of substrate and a simple hide. It was also commonplace to keep enclosures relatively small, because of the (now disproven) idea that a relatively large enclosure full of decor and multiple hides would stress a tarantula out, and make it difficult to locate its prey. 
These minimalist setups probably played a significant role in building the OBT's image as a highly defensive spider, as a recent study suggests its defensive behaviour is strongly influenced by enclosure layout.
When terrestrial (moderately thick layer of substrate, allowing for shallow burrowing, and a small horizontal hide), arboreal (thin layer of substrate with a large, vertical piece of bark for the animal to hide behind) and fossorial (very thick layer of substrate allowing for deep burrowing) setups were compared for keeping OBTs, the occurrence of defensive behaviours and bites was found to be highest in spiders kept in terrestrial setups, lower in arboreal setups, and lowest in fossorial ones.

Pterinochilus murinus is a skittish species, which will dig or web itself a secluded retreat it seldom wanders far from, and runs for cover at the slightest disturbance. 
However, exposed or cornered and unable to hide, it is prompt to react defensively, and will not hesitate to bite.

 

The OBT generally stays close to its burrow or retreat, ready to disappear inside at the slightest sign of danger

Thus, access to multiple deep, secure hides, such as a burrow or bark tubes, seems to considerably improve the spider's disposition.

Unsurprisingly, this amounts to providing the OBT with the living conditions it looks for in the wild.

Providing a captive P.murinus with the living conditions it would seek out in the wild significantly helps mitigating its defensiveness

The OBT in the wild 

Pterinochilus murinus inhabits an immense range that spans across most of East Africa, encompassing Kenya, Tanzania (including the island of Zanzibar), Malawi, Zambia, Zimbabwe and Mozambique, and extending west into eastern Angola. 
Across this immense territory, the species sports an impressive diversity of populations and locales, with a variety of colour morphs. Although the orange forms are the most famous and widespread in the hobby, and gave the species its common name, they only occur in small, localised populations in Kenya, mainland Tanzania and Zanzibar. 

The "Usambara Mountain Variant" is one of the orange morphs, from mainland Tanzania

 

Besides the iconic but uncommon fiery variants, there is also a plethora of golden, tan, and bronze forms, as well as darker forms (DCF), which often have very dark legs with pale rings; the most common in the southern fringes of its range in Zimbabwe and southern Zambia, is a stunning grey and black form, radically different from the stereotypical "orange baboon spider".

 

The many "dark colour forms", like this 'Mikumi DCF', sport dark legs with pale rings, looking very different from the orange ones

 

Throughout its range, Pterinochilus murinus occurs in a huge variety of biomes, from seasonally scorched savanna to lush forests. While it is usually kept in dry conditions (which isn't wrong, generations of keepers have had thriving OBTs in dry enclosures), some of the environments it inhabits are actually quite humid, such as the afromontane forests (a type of highland subtropical forest unique to Africa) on the slopes of Tanzanian and Kenyan mountain ranges. Even the more open biomes it inhabits are seasonally humid; the parched savannahs made famous by wildlife documentaries only look like that during the dry season, and are lush and green for a large part of the year. 

The OBT is an incredibly versatile species that can adapt to a variety of living conditions. This incredible adaptability also shows in its choice of microhabitat: it can choose to live in deep burrows in the ground, particularly on cliff faces and road embankments, make itself a burrow between tree roots that opens on a silk tunnel on the trunk, or even live fully arboreally in a tree hole, way above the ground. As it can just as well live in a tree cavity as in an underground burrow, it is one of the very few true "semi-arboreal" (a word often used very loosely and improperly in the hobby) tarantula species.

However, regardless of the place where it chooses to settle, there are consistent elements in the OBT's lifestyle. The hide it chooses, burrow or tree trunk, is secluded and enclosed on all sides except the entrances by solid walls of wood or dirt. 
In nature, the OBT rarely ever leaves this retreat, hunting with only its legs sticking out, or ambushed right in front of the entrance, ready to disappear into safety at the slightest sign of danger. Unlike some New World terrestrial species, it is not a tarantula that is ever seen patrolling the forest floor, away from its burrow (except, of course, for mature males wandering in search of a mate).

Even when hunting, the OBT rarely leaves the proximity of its retreat, either by lying in ambush right next to the entrance, or by sticking its legs out.

In captivity, this translates into providing a busy enclosure, with lots of hiding spots including hollow bark tubes large enough for the spider to hide its whole body inside, and/or a thick layer of substrate for burrowing.  Generous amounts of leaf litter is appreciated; the spider likes to weave it into its webbing and use them to extend the entrances or connect hides.

An example of enclosure layout for Pterinochilus murinus: deep substrate, a bark tube as a main hide, lots of dark corners to hide in, branches to anchor webbing and an abundance of leaf litter to weave into it

Given the right conditions to feel safe and mimic its wild lifestyle, the OBT is not more dangerous to keep that any other fast, skittish Old World tarantula species. While it is definitely a species that requires prior experience with fast tarantulas, it is a far cry from the hyper-aggressive ball of rage it is often claimed to be. 
In fact, this fabled monster was only created by the conditions it was kept in. Its legendary defensiveness is merely the understandable behaviour of a skittish animal which, deprived of the opportunity to hide, acting in the way any cornered, exposed wild animal would.

There may be two other factors to the OBT's reputation that have not been explored scientifically, but may have played a significant role. 
While this species, nowadays, is well established in the pet trade and captive-bred individuals are readily available, wild-caught specimens used to be commonplace in the early days in the hobby. 
It is possible (although uncertain) this may have worsened their defensiveness, as, not only were they often kept in unsuitable, bare enclosures, but they had literally been taken away from the familiar, secluded hide they were used to in the wild!

Nowadays, it is easy to find captive-bred OBTs, including many of the more unusual morphs

 Finally, because Pterinochilus murinus is a popular, readily available species, and often on the cheaper side, it is frequently picked as a first Old World tarantula. Unfortunately, among these keepers taking the leap into Old World species, is a significant chunk who are overestimating their level of experience, and insufficiently prepared to deal with that kind of speed and attitude. 
While it is not much harder to manage than most other Old World species, one is in for quite a shock if all they've known before were slow, docile beginner-friendly species!